Season the rice flour with salt and pepper, lightly dredge the shrimp in the flour; tap off excess. Heat peanut oil in a skillet until very hot. Add the coated shrimp to the hot oil and cook about 2 minutes each side. Add the mussels, asparagus tips, and shiitakes. Cook for 2 minutes just until heated through. Strain the sauce over the shellfish and vegetables. Poach the Udon noodles in hot salted water, drain and place in a warm bowl. Add the shellfish sauce. Top with pea tendrils, herbs, cashews, and sprouts.